Catatan_Kuliah II

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Stereoisomer
Descriptor
Stereoisomer






Enantiomer
Diastereomer
Erythro, threo
Meso Compound
Epimer
Chiral Molecules With No Chiral Centers
Definitions



Stereoisomers – compounds with the same
connectivity, different arrangement in space
Enantiomers – stereoisomers that are nonsuperimposible mirror images; only properties
that differ are direction (+ or -) of optical
rotation
Diastereomers – stereoisomers that are not
mirror images; different compounds with
different physical properties
enantiomer
Erythro dan threo
Diastereomer:
Stereoisomer yang bukan
pasangan enantiomer
1 dan 2 enantiomer
3 dan 4 juga enantiomer
Diastereomer: 1-3; 1-4; 2-3 dan 2-4
Epimers:
distereomer yang berbeda hanya
pada satu pusat kiral saja
OH
OH
HO
OH
HO
OH
HO
OH
HO
OH
OH
OH
Senyawa meso
Chiral Molecules With
No Chiral Centers
Allenes can be Chiral
H
Cl
H
C
C
H
C
C
CH3
CH3
C
C
H
Cl
Mycomycin, an antibiotic
H
H
H C C C C
C
C
C
CH=CHCH=CHCH2CO2H
o
Nocardia acidophilus []D = -130
PPh2
PPh2
(S)-BINAP
PPh2
PPh2
(R)-BINAP
Specifying Configuration (Chirality);
Cahn-Ingold-Prelog Notation


Specifies the "configuration" at each chiral
center, equivalent to "cis-" and "trans-" etc.
Abbreviated rules




Assign priorities to groups attached to chiral center
according to atomic # (same as Z/E rules)
Compare 2nd, 3rd etc. atom from center as
necessary, look for first point of difference
Multiple bonds "add up"
Determine direction of rotation 1 > 2 > 3 looking with
#4 group pointing "away"
Prioritize Using Cahn-Ingold-Prelog
Rules



Look at atoms directly attached to chirality center
 a) higher atomic number = higher priority
 b) heavier isotopes = higher priority
If no difference at first attached atom, move
along the chain until the first point of difference.
Multiple-bonded atoms are equivalent to the
same number of single-bonded atoms.
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